Does it really seem that reasonable though that a complete psychopath like this would become a Starfleet Admiral?

I don't see where all admirals have always been corrupt or evil. Admiral Hanson from Best of Both Worlds seemed alright. And the blonde admiral from TNG seemed normal enough.

This guy is just a bit over the top imo.

Weller was wonderful as the character, son. Shit, he stole the show when he was on screen. I bet that bastard brushed his teeth with bourbon, son.

The thing that should scare folks is that he was not a psychopath. I once posted in some thread that he reminded me of Curtis LeMay. Someone (M'Sharak?) responded that Weller, himself mentioned LeMay as someone who influenced his character. LeMay was incredibly respected as a general and was pivotal to U.S. success in the air war in Europe and the Pacific in World War II. If he had had his way, he also would've started a pre-emptive nuclear war to defeat the USSR in the early 1960s even though he knew millions would die. Marcus was distressingly close to art imitating life.

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I think the interview originally appeared at StarTrek.com, but Weller's answer regarding Lemay as a model for the Marcus character and characterization was quoted in this TrekToday piece. It's not long, so I'll quote it here:

TrekToday wrote:

According to Peter Weller, Star Trek into Darkness‘ Admiral Marcus is not dissimilar from a relatively unknown historical figure from the early 1960s.

Like that historical figure, the admiral wanted to strike first and take the advantage that doing so would bring.

“Marcus is no different than Curtis LeMay, with a conscience,” said Weller. “I don’t know if people remember who Curtis LeMay [was], but he hid eighteen nuclear missiles from President John F. Kennedy. He was the guy who wanted to pull the trigger on the Cuban Missile Crisis. If you see Fog of War, it was all about ‘First strike! First strike!’ That’s a warmonger. So these warmongers exist, man, and LeMay personifies that. They were real. They are real. The thing that Marcus doesn’t have is faith in the pacifistic attitude of this particular terrestrial organization because the Klingons are aggressive. A war is coming. They’re encroaching. And what Marcus is thinking is he wants to get a jump on them, just like Curtis LeMay. Anybody who is critical of this, just watch the Errol Morris documentary Fog of War. It’s from 2003, and listen to [Robert McNamara] talk about LeMay.”

“Here are the facts,” said Weller, “as Marcus sees them: ‘The Klingons are coming. They’re aggressive. I don’t believe in the pacifistic whoo-ha, touchy-feely, go-out-five-years-and-explore-brave-new-worlds …horseshit. There’s a war coming on.’ So what I do is I take out the plutonium nukes, if you will, called Khan. I take them out. And I made a mistake. I even say it. So I don’t know what people are missing. He’s a guy who did it, by his own conscience, to protect his own particular world and then realizes that he fucked up. Now, the thing that makes him bad, from a moralistic view, is that he’s willing to sacrifice Kirk and the Enterprise to put this thing back in its shell. And he feels that’s a calculated risk. ‘I was never going to spare your crew.’”

__________________As for literary criticism in general: I have long felt that any reviewer who expresses rage and loathing for a novel or a play or a poem is preposterous. He or she is like a person who has put on full armor and attacked a hot fudge sundae or a banana split. ~ Kurt Vonnegut, Jr.